My heater stays on even when I switch to A/C and the temperature is cranked all the way cold. Do yall think it is something as simple as the switch might be bad? Or have yall ever heard of someone have this problem and what did they do? The switch will work every now and then if you turn it just right. This problem is on my 1999 f-250 LD.

I am going to replace the switch and I will let you know. The switch is only $15. I called ford and they said it is either the switch or another part that requires the whole dash to be taken out to get to. I am hoping it is only the switch.

There is a heater blend door actuator that is controlled by the heat switch. The blend door actuator is under the Plenum. It is a PITA but you do not remove the dash to get to it. If it is defective it will also cause what you are describing. I would check it out before pulling the dash out to replace the blend door.

did you ever figure out the problem with your heater and stuff? I also have a F250 LD 1999 and my heater doesnt work but this is because of my reverse lights. Every time i go in reverse my fuse blows for reverse lights/ac controls/ heater controls. I cant seem to figure out the problem. Also my friend has the same truck as us and this just recently started happening to him too....

Yeah I took it to a dealership because it was a free diagnosis and it turned out to be the blend door was broken. It is like a $30 part, but you have to take the whole dash apart to get to it. It was pretty pricey to let someone else do it, but I just didn''t have the time.

had the same prob on my old 98 i just removed the blend door actuater put a wood screw and lil piece of flat metel as a handle with a zip tie to hold it in place pain in the a** during season changes but much cheaper the removing the dash
it worked but you only got max heat *or* max cold